This invention relates to electronic test devices and more particularly to test devices used in the telecommunications industry. The device of this invention is particularly useful for determining the current level and continuity in telephone loops.
A typical telephone loop or line consists of a pair of wires or conductors that provide a circuit or transmission path between the telephone company central office (C.O.) and the customer or subscriber premises. The loop allows the transmission of voice and data signals between telecommunications equipment at the central office, and customer premises equipment such as telephone handsets, PBX equipment, KEY equipment, computers, and facsimile equipment. Properly operating telephone loops have between approximately 23 milliamps and 35 milliamps of current. Less than 23 milliamps of line current may cause poor signal transmission, ghost rings, wrong numbers or other problems. More than 35 milliamps may cause problems such as cutoffs, burn-out of telephone equipment circuits, "squeal" or "hollow" sounds on the line, or other malfunctions.
The telephone loop extends form the central office to the customer premises where it typically terminates at an interface terminal or block which has multiple connectors for hook-up of the above-described customer equipment. Alternatively, the terminal may have a modular connector such as a plug or jack. The terminal serves as a demarcation point at which maintenance responsibility is divided; the telephone company having responsibility for maintenance of hardware from the terminal to the central office, and the customer having responsibility from the terminal to the customer equipment. Test equipment which determines the condition of the loop and the customer equipment is typically connected directly at the terminal.
Presently, telephone company personnel commonly test loops for continuity using, for example, an analog or digital multimeter. However, the expansion of telecommunication networks and their increased use for data transmission has resulted in complex loop interconnect wiring installations at interface terminals. And, testing such installations via a multimeter or the like is very time consuming and does not lend itself to an established procedure for technicians to follow. Also, such prior art techniques usually require two technicians using two meter devices or the like. Further, some test devices are incapable of testing both loop continuity and current level or are otherwise limited in use.
Thus, there has arisen a need in the telecommunications industry for a unitary apparatus and method of testing which simplify the proper identification and evaluation of telephone loops on a broad range of telecommunication systems. Despite the need for a test device and method which overcome the limitations and problems of the prior art, none insofar as is known have been proposed or developed.